Method for modulating stem cell growth

ABSTRACT

In one embodiment, provided is a composition including a prostaglandin compound for modulating stem cell proliferation and/or differentiation in a mammalian subject. In another embodiment, the instant application is directed to a composition which includes a prostaglandin compound for modulating proliferation and/or differentiation of stem cells of a mammalian subject, in which the stem cells are contacted directly or indirectly with the composition of the invention.

CROSS REFERENCE TO THE RELATED APPLICATIONS

This is a continuation of application Ser. No. 12/388,048 filed Feb. 18,2009, which claims priority from U.S. Provisional Application No.61/029,713 filed Feb. 19, 2008, the contents of all of which areincorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a method and composition for modulatingstem cell growth.

BACKGROUND

Stem cells are undifferentiated, or immature cells that are capable ofgiving rise to multiple, specialized cell types and ultimately toterminally differentiated cells. Unlike any other cells, they are ableto renew themselves such that essentially an endless supply of maturecell types can be generated when needed. Due to this capacity forself-renewal, stem cells are therapeutically useful for the regenerationand repair of tissues and organs. Stem cells have the potential forproviding benefit in a variety of clinical settings.

Stem cells are classified according to their differentiation potentialas pluripotent and multipotent. Embryonic stem cells (ESC) arewell-known as a pluripotent stem cell, which can be differentiated intoalmost any type of cells in the organism. Multipotent stem cells such asbone marrow stem cells exist in the adult body. Although their growthand differentiation potential is limited, they are considered to playimportant roles in self-repair of damaged tissues. Translating theseadvantages of stem cells into clinical benefits faces many challenges,including efficient proliferation and differentiation into the desiredcell type(s), maintaining genetic stability during long-term culture andensuring the absence of potentially tumorigenic ESC from the finalproduct. Modulation of growth and differentiation with low molecularweight compounds is one of the solutions for these problems.

Prostaglandins (hereinafter, referred to as PG(s)) are members of classof organic carboxylic acids, which are contained in tissues or organs ofhuman or other mammals, and exhibit a wide range of physiologicalactivity. PGs found in nature (primary PGs) generally have a prostanoicacid skeleton as shown in the formula (A):

On the other hand, some of synthetic analogues of primary PGs havemodified skeletons. The primary PGs are classified into PGAs, PGBs,PGCs, PGDs, PGEs, PGFs, PGGs, PGHs, PGIs and PGJs according to thestructure of the five-membered ring moiety, and further classified intothe following three types by the number and position of the unsaturatedbond at the carbon chain moiety:

Subscript 1: 13,14-unsaturated-15-OH

Subscript 2: 5,6- and 13,14-diunsaturated-15-OH

Subscript 3: 5,6-, 13,14-, and 17,18-triunsaturated-15-OH.

Further, the PGFs are classified, according to the configuration of thehydroxyl group at the 9-position, into α type (the hydroxyl group is ofan α-configuration) and β type (the hydroxyl group is of aβ-configuration).

PGs are known to have various pharmacological and physiologicalactivities, for example, vasodilatation, inducing of inflammation,platelet aggregation, stimulating uterine muscle, stimulating intestinalmuscle, anti-ulcer effect and the like.

Some 15-keto (i.e., having oxo at the 15-position instead ofhydroxy)-PGs and 13,14-dihydro (i.e., having single bond between the 13and 14-position)-15-keto-PGs are known as the substances naturallyproduced by the action of enzymes during the metabolism of primary PGs.

However it is not known how the prostaglandin compound acts on the stemcells.

DISCLOSURE OF THE INVENTION

The present invention relates to a method for modulating stem cellproliferation and/or differentiation in a mammalian subject, whichcomprises administering to the subject in need thereof an effectiveamount of a prostaglandin compound.

The present invention also relates to a method for modulatingproliferation and/or differentiation of stem cells of a mammaliansubject, which comprises contacting said stem cells with an effectiveamount of a prostaglandin compound.

The present invention also relates to a composition for modulating stemcell proliferation and/or differentiation in a mammalian subject whichcomprises a prostaglandin compound.

The present invention also relates to a composition for modulatingproliferation and/or differentiation of stem cells of a mammaliansubject which comprises a prostaglandin compound, wherein the modulationis effected by contacting the composition with said stem cells.

The present invention relates to use of a prostaglandin compound for themanufacture of a pharmaceutical composition for modulating stem cellproliferation and/or differentiation in a mammalian subject.

The present invention relates to use of a prostaglandin compound for themanufacture of a pharmaceutical composition for modulating proliferationand/or differentiation of stem cells of a mammalian subject, wherein themodulation is effected by contacting the composition with said stemcells.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 represents result of Test Example 2, effect of Compound A(11-deoxy-13,14-dihydro-15-keto-16,16-difluoro-PGE₁) ointment onexcisional wound healing in diabetic mice.

The sections of the skin from the animals treated with ointment base(left panel) and Compound A ointment (right panel) were stained withanti-Ki67 antibody.

FIG. 2 represents result of Test Example 3, effect of(11-deoxy-13,14-dihydro-15-keto-16,16-difluoro-PGE₁) on the osteoblastdifferentiation of mesenchymal stem cells.

DETAILED DESCRIPTION OF THE INVENTION

The nomenclature of the prostaglandin compounds used herein is based onthe numbering system of the prostanoic acid represented in the aboveformula (A).

The formula (A) shows a basic skeleton of the C-20 carbon atoms, but thepresent invention is not limited to those having the same number ofcarbon atoms. In the formula (A), the numbering of the carbon atomswhich constitute the basic skeleton of the PG compounds starts at thecarboxylic acid (numbered 1), and carbon atoms in the α-chain arenumbered 2 to 7 towards the five-membered ring, those in the ring are 8to 12, and those in the ω-chain are 13 to 20. When the number of carbonatoms is decreased in the α-chain, the number is deleted in the orderstarting from position 2; and when the number of carbon atoms isincreased in the α-chain, compounds are named as substitution compoundshaving respective substituents at position 2 in place of the carboxygroup (C-1). Similarly, when the number of carbon atoms is decreased inthe ω-chain, the number is deleted in the order starting from position20; and when the number of carbon atoms is increased in the ω-chain, thecarbon atoms beyond position 20 are named as substituents.Stereochemistry of the compounds is the same as that of the aboveformula (A) unless otherwise specified.

In general, each of the terms PGD, PGE and PGF represents a PG compoundhaving hydroxy groups at positions 9 and/or 11, but in the presentspecification, these terms also include those having substituents otherthan the hydroxy group at positions 9 and/or 11. Such compounds arereferred to as 9-dehydroxy-9-substituted-PG compounds or11-dehydroxy-11-substituted-PG compounds. A PG compound having hydrogenin place of the hydroxy group is simply named as 9- or 11-deoxy-PGcompound.

As stated above, the nomenclature of the PG compounds is based on theprostanoic acid skeleton. However, in case the compound has a similarpartial structure as a prostaglandin, the abbreviation of “PG” may beused. Thus, a PG compound of which α-chain is extended by two carbonatoms, that is, having 9 carbon atoms in the α-chain is named as2-decarboxy-2-(2-carboxyethyl)-PG compound. Similarly, a PG compoundhaving 11 carbon atoms in the α-chain is named as2-decarboxy-2-(4-carboxybutyl)-PG compound. Further, a PG compound ofwhich ω-chain is extended by two carbon atoms, that is, having 10 carbonatoms in the ω-chain is named as 20-ethyl-PG compound. These compounds,however, may also be named according to the IUPAC nomenclatures.

Examples of the analogs (including substituted derivatives) orderivatives include a PG compound of which carboxy group at the end ofα-chain is esterified; a compound of which α-chain is extended;physiologically acceptable salt thereof; a compound having a double bondat 2-3 position or a triple bond at position 5-6, a compound havingsubstituent(s) at position 3, 5, 6, 16, 17, 18, 19 and/or 20; and acompound having lower alkyl or a hydroxy (lower) alkyl group at position9 and/or 11 in place of the hydroxy group.

According to the present invention, preferred substituents at position3, 17, 18 and/or 19 include alkyl having 1-4 carbon atoms, especiallymethyl and ethyl. Preferred substituents at position 16 include loweralkyl such as methyl and ethyl, hydroxy, halogen atoms such as chlorineand fluorine, and aryloxy such as trifluoromethylphenoxy. Preferredsubstituents at position 17 include lower alkyl such as methyl andethyl, hydroxy, halogen atoms such as chlorine and fluorine, aryloxysuch as trifluoromethylphenoxy. Preferred substituents at position 20include saturated or unsaturated lower alkyl such as C1-4 alkyl, loweralkoxy such as C1-4 alkoxy, and lower alkoxy alkyl such as C1-4alkoxy-C1-4 alkyl. Preferred substituents at position 5 include halogenatoms such as chlorine and fluorine. Preferred substituents at position6 include an oxo group forming a carbonyl group. Stereochemistry of PGshaving hydroxy, lower alkyl or hydroxy(lower)alkyl substituent atposition 9 and/or 11 may be α, β or a mixture thereof.

Further, the above analogs or derivatives may be compounds having analkoxy, cycloalkyl, cycloalkyloxy, phenoxy or phenyl group at the end ofthe ω-chain where the chain is shorter than the primary PGs.

A prostaglandin compound used in the present invention is represented bythe formula (I):

wherein L, M and N are hydrogen, hydroxy, halogen, lower alkyl,hydroxy(lower)alkyl, lower alkanoyloxy or oxo, wherein at least one of Land M is a group other than hydrogen, and the five-membered ring mayhave at least one double bond;

A is —CH₃, or —CH₂OH, —COCH₂OH, —COOH or a functional derivativethereof;

B is single bond, —CH₂—CH₂—, —CH═CH—, —C≡C—, —CH₂—CH₂—CH₂—, —CH═CH—CH₂—,—CH₂—CH═CH—, —C≡C—CH₂— or —CH₂—C≡C—;

Z is

or single bond

wherein R₄ and R₅ are hydrogen, hydroxy, halogen, lower alkyl, loweralkoxy or hydroxy(lower)alkyl, wherein R₄ and R₅ are not hydroxy andlower alkoxy at the same time;

R₁ is a saturated or unsaturated bivalent lower or medium aliphatichydrocarbon residue, which is unsubstituted or substituted with halogen,alkyl, hydroxy, oxo, aryl or heterocyclic group, and at least one ofcarbon atom in the aliphatic hydrocarbon is optionally substituted byoxygen, nitrogen or sulfur; and

Ra is a saturated or unsaturated lower or medium aliphatic hydrocarbonresidue, which is unsubstituted or substituted with halogen, oxo,hydroxy, lower alkyl, lower alkoxy, lower alkanoyloxy,cyclo(lower)alkyl, cyclo(lower)alkyloxy, aryl, aryloxy, heterocyclicgroup or hetrocyclic-oxy group; lower alkoxy; lower alkanoyloxy;cyclo(lower)alkyl; cyclo(lower)alkyloxy; aryl; aryloxy; heterocyclicgroup; heterocyclic-oxy group.

A preferred compound used in the present invention is represented by theformula (II):

wherein L and M are hydrogen atom, hydroxy, halogen, lower alkyl,hydroxy(lower)alkyl, lower alkanoyloxy or oxo, wherein at least one of Land M is a group other than hydrogen, and the five-membered ring mayhave one or more double bonds;

A is —CH₃, or —CH₂OH, —COCH₂OH, —COOH or a functional derivativethereof;

B is single bond, —CH₂—CH₂—, —CH═CH—, —C≡C—, —CH₂—CH₂—CH₂—, —CH═CH—CH₂—,—CH₂—CH═CH—, —C≡C—CH₂— or —CH₂—C≡C—;

Z is

or single bond

wherein R₄ and R₅ are hydrogen, hydroxy, halogen, lower alkyl, loweralkoxy or hydroxy(lower)alkyl, wherein R₄ and R₅ are not hydroxy andlower alkoxy at the same time;

X₁ and X₂ are hydrogen, lower alkyl, or halogen;

R₁ is a saturated or unsaturated bivalent lower or medium aliphatichydrocarbon residue, which is unsubstituted or substituted with halogen,alkyl, hydroxy, oxo, aryl or heterocyclic group, and at least one ofcarbon atom in the aliphatic hydrocarbon is optionally substituted byoxygen, nitrogen or sulfur;

R₂ is a single bond or lower alkylene; and

R₃ is lower alkyl, lower alkoxy, lower alkanoyloxy, cyclo(lower)alkyl,cyclo(lower)alkyloxy, aryl, aryloxy, heterocyclic group orheterocyclic-oxy group.

In the above formula, the term “unsaturated” in the definitions for R₁and Ra is intended to include at least one or more double bonds and/ortriple bonds that are isolatedly, separately or serially present betweencarbon atoms of the main and/or side chains. According to the usualnomenclature, an unsaturated bond between two serial positions isrepresented by denoting the lower number of the two positions, and anunsaturated bond between two distal positions is represented by denotingboth of the positions.

The term “lower or medium aliphatic hydrocarbon” refers to a straight orbranched chain hydrocarbon group having 1 to 14 carbon atoms (for a sidechain, 1 to 3 carbon atoms are preferable) and preferably 1 to 10,especially 1 to 8 carbon atoms.

The term “halogen atom” covers fluorine, chlorine, bromine and iodine.

The term “lower” throughout the specification is intended to include agroup having 1 to 6 carbon atoms unless otherwise specified.

The term “lower alkyl” refers to a straight or branched chain saturatedhydrocarbon group containing 1 to 6 carbon atoms and includes, forexample, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl,pentyl and hexyl.

The term “lower alkylene” refers to a straight or branched chainbivalent saturated hydrocarbon group containing 1 to 6 carbon atoms andincludes, for example, methylene, ethylene, propylene, isopropylene,butylene, isobutylene, t-butylene, pentylene and hexylene.

The term “lower alkoxy” refers to a group of lower alkyl-O—, whereinlower alkyl is as defined above.

The term “hydroxy(lower)alkyl” refers to a lower alkyl as defined abovewhich is substituted with at least one hydroxy group such ashydroxymethyl, 1-hydroxyethyl, 2-hydroxyethyl and1-methyl-1-hydroxyethyl.

The term “lower alkanoyloxy” refers to a group represented by theformula RCO—O—, wherein RCO— is an acyl group formed by oxidation of alower alkyl group as defined above, such as acetyl.

The term “cyclo(lower)alkyl” refers to a cyclic group formed bycyclization of a lower alkyl group as defined above but contains threeor more carbon atoms, and includes, for example, cyclopropyl,cyclobutyl, cyclopentyl and cyclohexyl.

The term “cyclo(lower)alkyloxy” refers to the group ofcyclo(lower)alkyl-O—, wherein cyclo(lower)alkyl is as defined above.

The term “aryl” may include unsubstituted or substituted aromatichydrocarbon rings (preferably monocyclic groups), for example, phenyl,tolyl, xylyl. Examples of the substituents are halogen atom andhalo(lower)alkyl, wherein halogen atom and lower alkyl are as definedabove.

The term “aryloxy” refers to a group represented by the formula ArO—,wherein Ar is aryl as defined above.

The term “heterocyclic group” may include mono- to tri-cyclic,preferably monocyclic heterocyclic group which is 5 to 14, preferably 5to 10 membered ring having optionally substituted carbon atom and 1 to4, preferably 1 to 3 of 1 or 2 type of hetero atoms selected fromnitrogen atom, oxygen atom and sulfur atom. Examples of the heterocyclicgroup include furyl, thienyl, pyrrolyl, oxazolyl, isoxazolyl, thiazolyl,isothiazolyl, imidazolyl, pyrazolyl, furazanyl, pyranyl, pyridyl,pyridazinyl, pyrimidyl, pyrazinyl, 2-pyrrolinyl, pyrrolidinyl,2-imidazolinyl, imidazolidinyl, 2-pyrazolinyl, pyrazolidinyl,piperidino, piperazinyl, morpholino, indolyl, benzothienyl, quinolyl,isoquinolyl, purinyl, quinazolinyl, carbazolyl, acridinyl,phenanthridinyl, benzimidazolyl, benzimidazolinyl, benzothiazolyl,phenothiazinyl. Examples of the substituent in this case includehalogen, and halogen substituted lower alkyl group, wherein halogen atomand lower alkyl group are as described above.

The term “heterocyclic-oxy group” means a group represented by theformula HcO—, wherein Hc is a heterocyclic group as described above.

The term “functional derivative” of A includes salts (preferablypharmaceutically acceptable salts), ethers, esters and amides.

Suitable “pharmaceutically acceptable salts” include conventionally usednon-toxic salts, for example a salt with an inorganic base such as analkali metal salt (such as sodium salt and potassium salt), an alkalineearth metal salt (such as calcium salt and magnesium salt), an ammoniumsalt; or a salt with an organic base, for example, an amine salt (suchas methylamine salt, dimethylamine salt, cyclohexylamine salt,benzylamine salt, piperidine salt, ethylenediamine salt, ethanolaminesalt, diethanolamine salt, triethanolamine salt,tris(hydroxymethylamino)ethane salt, monomethyl-monoethanolamine salt,procaine salt and caffeine salt), a basic amino acid salt (such asarginine salt and lysine salt), tetraalkyl ammonium salt and the like.These salts may be prepared by a conventional process, for example fromthe corresponding acid and base or by salt interchange.

Examples of the ethers include alkyl ethers, for example, lower alkylethers such as methyl ether, ethyl ether, propyl ether, isopropyl ether,butyl ether, isobutyl ether, t-butyl ether, pentyl ether and1-cyclopropyl ethyl ether; and medium or higher alkyl ethers such asoctyl ether, diethylhexyl ether, lauryl ether and cetyl ether;unsaturated ethers such as oleyl ether and linolenyl ether; loweralkenyl ethers such as vinyl ether, allyl ether; lower alkynyl etherssuch as ethynyl ether and propynyl ether; hydroxy(lower)alkyl etherssuch as hydroxyethyl ether and hydroxyisopropyl ether; lower alkoxy(lower)alkyl ethers such as methoxymethyl ether and 1-methoxyethylether; optionally substituted aryl ethers such as phenyl ether, tosylether, t-butylphenyl ether, salicyl ether, 3,4-di-methoxyphenyl etherand benzamidophenyl ether; and aryl(lower)alkyl ethers such as benzylether, trityl ether and benzhydryl ether.

Examples of the esters include aliphatic esters, for example, loweralkyl esters such as methyl ester, ethyl ester, propyl ester, isopropylester, butyl ester, isobutyl ester, t-butyl ester, pentyl ester and1-cyclopropylethyl ester; lower alkenyl esters such as vinyl ester andallyl ester; lower alkynyl esters such as ethynyl ester and propynylester; hydroxy(lower)alkyl ester such as hydroxyethyl ester; loweralkoxy (lower) alkyl esters such as methoxymethyl ester and1-methoxyethyl ester; and optionally substituted aryl esters such as,for example, phenyl ester, tolyl ester, t-butylphenyl ester, salicylester, 3,4-di-methoxyphenyl ester and benzamidophenyl ester; andaryl(lower)alkyl ester such as benzyl ester, trityl ester and benzhydrylester.

The amide of A mean a group represented by the formula —CONR′R″, whereineach of R′ and R″ is hydrogen, lower alkyl, aryl, alkyl- oraryl-sulfonyl, lower alkenyl and lower alkynyl, and include for examplelower alkyl amides such as methylamide, ethylamide, dimethylamide anddiethylamide; arylamides such as anilide and toluidide; and alkyl- oraryl-sulfonylamides such as methylsulfonylamide, ethylsulfonyl-amide andtolylsulfonylamide.

Preferred examples of L and M include hydrogen, hydroxy and oxo, andespecially, M is hydroxy and L is oxo which has a 5-membered ringstructure of, so called, PGE type.

Preferred example of A is —COOH, its pharmaceutically acceptable salt,ester or amide thereof.

Preferred example of X₁ and X₂ are both being halogen atoms, and morepreferably, fluorine atoms, so called 16,16-difluoro type.

Preferred R₁ is a hydrocarbon residue containing 1-10 carbon atoms,preferably 6-10 carbon atoms. Further, at least one carbon atom in thealiphatic hydrocarbon is optionally substituted by oxygen, nitrogen orsulfur. Examples of R₁ include, for example, the following groups

-   -   —CH₂—CH₂—CH₂—CH₂—CH₂—CH₂—,    -   —CH₂—CH═CH—CH₂—CH₂—CH₂—,    -   —CH₂—CH₂—CH₂—CH₂—CH═CH—,    -   —CH₂—C≡C—CH₂—CH₂—CH₂—,    -   —CH₂—CH₂—CH₂—CH₂—O—CH₂—,    -   —CH₂—CH═CH—CH₂—O—CH₂—,    -   —CH₂—C≡C—CH₂—O—CH₂—,    -   —CH₂—CH₂—CH₂—CH₂—CH₂—CH₂—CH₂—,    -   —CH₂—CH═CH—CH₂—CH₂—CH₂—CH₂—,    -   —CH₂—CH₂—CH₂—CH₂—CH₂—CH═CH—,    -   —CH₂—C≡C—CH₂—CH₂—CH₂—CH₂—,    -   —CH₂—CH₂—CH₂—CH₂—CH₂—CH(CH₃)—CH₂—,    -   —CH₂—CH₂—CH₂—CH₂—CH(CH₃)—CH₂—,    -   —CH₂—CH₂—CH₂—CH₂—CH₂—CH₂—CH₂—CH₂—,    -   CH₂—CH═CH—CH₂—CH₂—CH₂—CH₂—CH₂—,    -   —CH₂—CH₂—CH₂—CH₂—CH₂—CH₂—CH═CH—,    -   —CH₂—C≡C—CH₂—CH₂—CH₂—CH₂—CH₂—, and    -   —CH₂—CH₂—CH₂—CH₂—CH₂—CH₂—CH(CH₃)—CH₂—.

Preferred Ra is a hydrocarbon containing 1-10 carbon atoms, morepreferably, 1-8 carbon atoms. Ra may have one or two side chains havingone carbon atom.

Preferable compounds include Ra is substituted by halogen and/or Z isC═O in the formula (I), or one of X1 and X2 is substituted by halogenand/or Z is C═O in the formula (II).

Most preferred embodiment is a prostaglandin compound is11-deoxy-13,14-dihydro-15-keto-16,16-difluoro-prostaglandin E₁ compound.

The configuration of the ring and the α- and/or ω chains in the aboveformula (I) and (II) may be the same as or different from that of theprimary PGs. However, the present invention also includes a mixture of acompound having a primary type configuration and a compound of anon-primary type configuration.

In the present invention, the PG compound which is dihydro between 13and 14, and keto(═O) at 15 position may be in the keto-hemiacetalequilibrium by formation of a hemiacetal between hydroxy at position 11and keto at position 15.

For example, it has been revealed that when both of X₁ and X₂ arehalogen atoms, especially, fluorine atoms, the compound contains atautomeric isomer, bicyclic compound.

If such tautomeric isomers as above are present, the proportion of bothtautomeric isomers varies with the structure of the rest of the moleculeor the kind of the substituent present. Sometimes one isomer maypredominantly be present in comparison with the other. However, it is tobe appreciated that the present invention includes both isomers.

Further, the 15-keto-PG compounds used in the invention include thebicyclic compound and analogs or derivatives thereof.

The bicyclic compound is represented by the formula (III)

wherein, A is —CH₃, or —CH₂OH, —COCH₂OH, —COOH or a functionalderivative thereof;

X₁′ and X₂′ are hydrogen, lower alkyl, or halogen;

Y is

wherein R₄′ and R₅′ are hydrogen, hydroxy, halogen, lower alkyl, loweralkoxy or hydroxy(lower)alkyl, wherein R₄′ and R₅′ are not hydroxy andlower alkoxy at the same time.

R₁ is a saturated or unsaturated divalent lower or medium aliphatichydrocarbon residue, which is unsubstituted or substituted with halogen,alkyl, hydroxy, oxo, aryl or heterocyclic group, and at least one ofcarbon atom in the aliphatic hydrocarbon is optionally substituted byoxygen, nitrogen or sulfur; and

R₂′ is a saturated or unsaturated lower or medium aliphatic hydrocarbonresidue, which is unsubstituted or substituted with halogen, oxo,hydroxy, lower alkyl, lower alkoxy, lower alkanoyloxy,cyclo(lower)alkyl, cyclo(lower)alkyloxy, aryl, aryloxy, heterocyclicgroup or hetrocyclic-oxy group; lower alkoxy; lower alkanoyloxy;cyclo(lower)alkyl; cyclo(lower)alkyloxy; aryl; aryloxy; heterocyclicgroup; heterocyclic-oxy group.

R₃′ is hydrogen, lower alkyl, cyclo(lower)alkyl, aryl or heterocyclicgroup.

Furthermore, while the compounds used in the invention may berepresented by a formula or name based on keto-type regardless of thepresence or absence of the isomers, it is to be noted that suchstructure or name does not intend to exclude the hemiacetal typecompound.

In the present invention, any of isomers such as the individualtautomeric isomers, the mixture thereof, or optical isomers, the mixturethereof, a racemic mixture, and other steric isomers may be used in thesame purpose.

Some of the compounds used in the present invention may be prepared bythe method disclosed in U.S. Pat. Nos. 5,073,569, 5,166,174, 5,221,763,5,212,324, 5,739,161 and 6,242,485 (these cited references are hereinincorporated by reference).

An embodiment of the present invention includes a method for modulatingstem cell proliferation and/or differentiation in a mammalian subject,which comprises administering to the subject in need thereof aneffective amount of a prostaglandin compound.

The mammalian subject may be any mammalian subject including a human.The subject in need of the modulation of stem cell proliferation and/ordifferentiation may include, but not limited to, those suffered from adisease or condition in which the tissue or organ is damaged ordefective. For example, the mammalian subject may be those suffered fromosteoporosis, bone fracture, alveolar bone regeneration, anaplasticanemia and muscular dystrophy. Accordingly, the present invention alsoprovides a method for the treatment of a disease or condition in whichthe tissue or organ is damaged or defective, for example, for thetreatment of osteoporosis, bone fracture, alveolar bone regeneration,anaplastic anemia and muscular dystrophy.

The compound may be applied systemically or topically. Usually, thecompound may be administered by oral administration, intranasaladministration, inhalational administration, intravenous injection(including infusion), subcutaneous injection, intra rectaladministration, intra vaginal administration, transdermal administrationand the like.

The dose may vary depending on the strain of the animal, age, bodyweight, symptom to be treated, desired therapeutic effect,administration route, term of treatment and the like. A satisfactoryeffect can be obtained by systemic administration 1-4 times per day orcontinuous administration at the amount of 0.00001-500 mg/kg per day,more preferably 0.0001-100 mg/kg.

The compound may preferably be formulated in a pharmaceuticalcomposition suitable for administration in a conventional manner. Thecomposition may be those suitable for oral administration, intranasaladministration, inhalational administration, injection or perfusion aswell as it may be an external agent, suppository or pessary.

The composition of the present invention may further containphysiologically acceptable additives. Said additives may include theingredients used with the present compounds such as excipient, diluent,filler, resolvent, lubricant, adjuvant, binder, disintegrator, coatingagent, cupsulating agent, ointment base, suppository base, aerozolingagent, emulsifier, dispersing agent, suspending agent, thickener,tonicity agent, buffering agent, soothing agent, preservative,antioxidant, corrigent, flavor, colorant, a functional material such ascyclodextrin and biodegradable polymer, stabilizer. The additives arewell known to the art and may be selected from those described ingeneral reference books of pharmaceutics.

The amount of the above-defined compound in the composition of theinvention may vary depending on the formulation of the composition, andmay generally be 0.000001-10.0%, more preferably 0.00001-5.0%, mostpreferably 0.0001-1%.

Examples of solid compositions for oral administration include tablets,troches, sublingual tablets, capsules, pills, powders, granules and thelike. The solid composition may be prepared by mixing one or more activeingredients with at least one inactive diluent. The composition mayfurther contain additives other than the inactive diluents, for example,a lubricant, a disintegrator and a stabilizer. Tablets and pills may becoated with an enteric or gastroenteric film, if necessary. They may becovered with two or more layers. They may also be adsorbed to asustained release material, or microcapsulated. Additionally, thecompositions may be capsulated by means of an easily degradable materialsuch gelatin. They may be further dissolved in an appropriate solventsuch as fatty acid or its mono, di or triglyceride to be a soft capsule.Sublingual tablet may be used in need of fast-acting property.

Examples of liquid compositions for oral administration includeemulsions, solutions, suspensions, syrups and elixirs and the like. Saidcomposition may further contain a conventionally used inactive diluentse.g. purified water or ethyl alcohol. The composition may containadditives other than the inactive diluents such as adjuvant e.g. wettingagents and suspending agents, sweeteners, flavors, fragrance andpreservatives.

The composition of the present invention may be in the form of sprayingcomposition, which contains one or more active ingredients and may beprepared according to a known method.

Example of the intranasal preparations may be aqueous or oily solutions,suspensions or emulsions comprising one or more active ingredient. Forthe administration of an active ingredient by inhalation, thecomposition of the present invention may be in the form of suspension,solution or emulsion which can provide aerosol or in the form of powdersuitable for dry powder inhalation. The composition for inhalationaladministration may further comprise a conventionally used propellant.

Examples of the injectable compositions of the present invention forparenteral administration include sterile aqueous or non-aqueoussolutions, suspensions and emulsions. Diluents for the aqueous solutionor suspension may include, for example, distilled water for injection,physiological saline and Ringer's solution.

Non-aqueous diluents for solution and suspension may include, forexample, propylene glycol, polyethylene glycol, vegetable oils such asolive oil, alcohols such as ethanol and polysorbate. The composition mayfurther comprise additives such as preservatives, wetting agents,emulsifying agents, dispersing agents and the like. They may besterilized by filtration through, e.g. a bacteria-retaining filter,compounding with a sterilizer, or by means of gas or radioisotopeirradiation sterilization. The injectable composition may also beprovided as a sterilized powder composition to be dissolved in asterilized solvent for injection before use.

The present external agent includes all the external preparations usedin the fields of dermatology and otolaryngology, which includesointment, cream, lotion and spray.

Another form of the present invention is suppository or pessary, whichmay be prepared by mixing active ingredients into a conventional basesuch as cacao butter that softens at body temperature, and nonionicsurfactants having suitable softening temperatures may be used toimprove absorbability.

Another embodiment of the present invention includes a method formodulating proliferation and/or differentiation of stem cells of amammalian subject, which comprises contacting said stem cells with aneffective amount of a prostaglandin compound.

The method can be used on cells in culture, e.g. in vitro or ex vivo.For example, stem cells or progenitor cells can be cultured in vitro inculture medium and the contacting step can be effected by adding one ormore prostaglandin compounds to the culture medium in a amountsufficient to modulate one or more of proliferation, survival and/ordifferentiation, e.g. at the amount of 1×10⁻¹²-1×10⁻³ mol/l. Accordingto the present invention, the cells may be contacted concomitantly withthe compound of the present invention and the one or more stem cellmodulators, or the cells may be contacted sequentially.

The method of modulating stem cell proliferation and/or differentiationmay further comprise administering to the subject with one or more stemcell modulators in order to modulate proliferation and/ordifferentiation the stem cells.

The method of the present invention can be used to stimulate the ex vivoexpansion and/or differentiation of stem cells and thereby provide apopulation of cells suitable for transplantation or administration to asubject in need thereof. Ex vivo expansion of stem cells has therapeuticindications for treating numerous disease conditions.

The method of modulating proliferation and/or differentiation of stemcells may also be used in vivo to modulate proliferation and/ordifferentiation of resident stem cells in tissues and thereby aid in thereplacement or repair of tissue damaged as a result of the disease ordisorder, or after surgery or injury and so on.

Sequential methods that modulate proliferation and subsequentdifferentiation of stem cells are also contemplated. For example, a stemcell population may be expanded ex vivo by contacting the cells,directly or indirectly, with a prostaglandin compound.

The method of the present invention may be employed in the regenerationtherapy. The expanded population of cells is subsequently administeredto a subject and treated in vivo with one or more stem cell modulatorsthat promotes differentiation of the stem cells in situ. Alternatively,both steps may be conducted ex vivo prior to administration of the cellsto a subject.

For in vivo and ex vivo methods, the stem cells can be autologous,allogeneic or xenogeneic.

Therapeutic applications of the method typically pertain to situationswhere there is a need to replace lost or damaged tissue, for example,after chemotherapy or radiation therapy, after muscle or skin injury, orin the treatment or management of diseases and disorders. For example,the methods can be used in the treatment, management or prevention ofneurodegenerative disorders, such as degenerative bone diseases such asosteoporosis; bone fracture, alveolar bone regeneration; anaplasticanemia and muscular dystrophy.

The term “stem cell modulator” as used herein, refers to a compound thatis capable of stimulating or inhibiting stem cell proliferation,differentiation, or both proliferation and differentiation.

The term “stem cell” as used herein, includes human origin or stem cellsof non-human mammalian origin and refers to a cell that is capable ofdifferentiating into one or more differentiated cell types. The stemcells may be pluripotent stem cells having the capacity to develop intoany cell type, or they may be multipotent stem cells having the capacityto differentiate into several different, final differentiated cell typesand derived from a particular tissue or organ, for example, from blood,nerve, skeletal muscle, cardiac muscle, bone marrow, skin, gut, bone,kidney, liver, pancreas, thymus, and the like. Pluripotent stem cellsare usually embryonic stem cells in origin and multipotent stem cellsinclude somatic stem cells such as mesenchymal stem cells, bone marrowstem cells, adipose derived stem cells, hemopoietic stem cells,epidermal stem cells and neuronal stem cells. According to the instantinvention, stem cells may preferably be neuronal stem cells, epidermalstem cells and mesenchymal stem cells.

The term “progenitor cell” as used herein, refers to a cell that iscommitted to a particular cell lineage and which gives rise to aparticular limited range of differentiated cell types by a series ofcell divisions. An example of a progenitor cell would be amyoblast,which is capable of differentiation to only one type of cell, but isitself not fully mature or fully differentiated.

The terms “proliferation” as used interchangeably herein with referenceto cells, refer to an increase in the number of cells of the same typeby cell division.

The term “differentiation” as used herein, refers to a developmentalprocess whereby cells become specialized for a particular function, forexample, where cells acquire one or more morphological characteristicsand/or functions different from that of the initial cell type.

The pharmaceutical composition of the present invention may furthercontain other pharmacological ingredients as far as they do notcontradict the purpose of the present invention.

Further details of the present invention will follow with reference totest example, which, however, is not intended to limit the presentinvention.

Test Example 1

The effect of Compound A(11-deoxy-13,14-dihydro-15-keto-16,16-difluoro-PGE₁) on impaired neuronwas tested. 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine hydrochloride(MPTP) was intraperitoneally administered to male C57BL/6 mice aged 10weeks at 15 mg/kg/dose 4 times a day with an approximately 3-hourinterval between doses for 2 days (experimental Day 1 and Day 2) todestroy the dopaminergic neuron in the brain. On the day following thefinal MPTP administration (on Day 3), some MPTP-treated mice weresacrificed to estimate the severity of degeneration and loss ofnigro-striatal dopamine neurons by measuring the area of tyrosinehydroxylase (TH)-positive immunostained fibers in striatum. OtherMPTP-treated mice were orally administered Compound A(11-deoxy-13,14-dihydro-15-keto-16,16-difluoro-PGE₁) or the vehicletwice a day for 5 days (from Day 3 to Day 7) starting from the dayfollowing the final MPTP administration. The mice were decapitated onthe day following the final administration of Compound A or the vehicle(on Day 8), and the whole brain was removed by incision of the skull,and placed into Bouin's fluid (pH 3.5-4.0). The brain section at thelevel of striatum (0.74 mm anterior to bregma) and substantia nigra(3.08 mm posterior to bregma) was cut out. After dehydration, theparaffin embedding of the slices was employed. Sections (about 6 μmthick) were prepared out of each of the slices at Bregma 0.74 mm andBregma −3.08 mm, and the sections were used for TH immunostaining. Thenumber of TH-positive immunostained cells in the right substantia nigracompacta (SNC) at Bregma −3.08 mm was counted by visual observationusing an optical microscope OLYMPUS BH-2 (Olympus Corp.) with a ×20microscope objective. For measuring the area of TH-positiveimmunostained fibers in striatum, an image obtained with an opticalmicroscope OLYMPUS BH-2 (Olympus Corp.) with a ×40 microscope objectiveof TH-positive immunostained fibers in the right caudate putamen (CPu)at Bregma 0.74 mm was incorporated into a computer through OLYMPUSMCD-350, and the area of TH-positive fibers larger than 5 μm² wasmeasured using an image analyzer Win ROOF (V5.6, Mitani Corp.), andexpressed in term of an area of 1 mm².

On the day following the final MPTP administration (on Day 3), theMPTP-treated mice already showed a significant decrease in the area ofTH-positive immunostained fibers in the striatum (0.0168±0.0029 mm²) ascompared to the normal mice (0.0758±0.0182 mm²), and thus thedegeneration and loss of the nigro-striatal dopaminergic neurons werealready observed on Day 3 by the MPTP treatment for 2 days.

As shown in Table 1, after the treatment period (on Day 8), asignificantly smaller area of TH-positive fibers in the striatum wasobserved in the “MPTP+Vehicle (control)” group compared to the“Physiological saline+Vehicle (control)” group. The area of the“MPTP+Vehicle (control)” group was similar to that observed in theMPTP-treated mice on Day 3. On the other hand, the “MPTP+Compound A at0.1 mg/kg” group and the “MPTP+Compound A at 1 mg/kg” group showed asignificantly greater mean area of TH-positive fibers in the striatumcompared to the “MPTP+Vehicle (control)” group.

As shown in Table 2, Compound A increased the number of TH-positiveimmunostained cells in the substantia nigra in a dose-dependent manner.

The results show that Compound A restores the impaired neuron. Furthermore, the results indicate that Compound A facilitates proliferation anddifferentiation of stem cells and regenerate the impaired tissues.

TABLE 1 Effects of oral administration of Compound A on area ofTH-positive immunostained fibers of striatum in the MPTP-treated mice.Area of TH-positive immunostained fibers in striatum (mm2), mean ± Groupn S.E. Physiological saline + 10 0.1432 ± 0.0223 Vehicle (Control)MPTP + Vehicle (Control) 10 0.0117 ± 0.0029** MPTP + Compound A at 0.110 0.0465 ± 0.0102## mg/kg MPTP + Compound A at 1 10 0.0444 ± 0.0092##mg/kg

TABLE 2 Effects of oral administration of Compound A on number ofTH-positive immunostained cells of substantia nigra in the MPTP-treatedmice. TH-positive immunostained cells in substantia nigra (Number ofcells ), mean ± Group n S.E. Physiological saline + 10 54.1 ± 2.7Vehicle (Control) MPTP + Vehicle (Control) 10 34.2 ± 5.0** MPTP +Compound A at 0.1 10 35.2 ± 5.0 mg/kg MPTP + Compound A at 1 10 44.4 ±5.0 mg/kg

Test Example 2

The effect of Compound A(11-deoxy-13,14-dihydro-15-keto-16,16-difluoro-PGE₁) on excisional woundhealing was tested. A full-thickness excisional wound (1.5×1.5 cm) wasmade on the back of female diabetic (BKS.Cg-+Lepr^(db)/+Lepr^(db)/Jcl)mice at the age of 12 weeks. The excisional wound was covered with theperforated film dressing. Each test ointment was put into a 1-mLdisposable polypropylene syringe to which a 21G hypodermic needle isattached, and 0.1 mL of the test ointment was applied to the wound bysticking the hypodermic needle into the film dressing, which covers theexcisional wound. The application was performed once a day for 21 daysstarting from the day when the excisional wound was made; the day whenthe excisional wound was made was defined as Day 1. For histologicalexamination, the skin including the excisional wound was obtained fromanimals treated with each test ointment for 6 days, and was served forimmunostaining with antibody against Ki67, a marker protein ofproliferating cells. The outline of each excisional wound was tracedbefore application (Day 1) and Days 6, 8, 11, 13, 15, 18, 20, and 22 ofadministration. The traced excisional wound area was measured with anarea-line meter. The wound area on each day of measurement was expressedas a ratio of the wound area on Day 1 as 100%, and the area under thewound area (%)-time curve (AUC) was calculated by using a trapezoidmethod.

Marked increase of proliferating (Ki67-positive) cells in the epidermiswas observed in the Compound A ointment group than the ointment basegroup (FIG. 1). Since the epidermis is believed to contain only twotypes of proliferating cells: stem cells and their transit amplifyingprogeny (transit amplifying cells), this result indicates that CompoundA stimulated proliferation of stem cells or differentiation to theirprogeny.

With such stimulatory activity, Compound A accelerated skin woundhealing (Table 3).

TABLE 3 Effect of Compound A ointment on excisional wound healing indiabetic mice. Concentration AUC_(Day1-22) Group micro-g/g n Mean ± S.E.Ointment base — 10 1168.8 ± 42.4 Compound A 10 10  965.4 ± 26.4**ointment Compound A 100 10  988.0 ± 22.0* ointment *p < 0.05, **p < 0.01compared with ointment base

Test Example 3

Effect of Compound A(11-deoxy-13,14-dihydro-15-keto-16,16-difluoro-PGE₁) on the osteoblastdifferentiation of mesenchymal stem cells was tested.

Method

Human bone marrow donor samples was obtained to initiate the productionof mesenchymal stem cell (MSC) for the study. The MSCs was then expandedin tissue culture flasks. The Compound A in DMSO and kept frozen at −20°C. until used, were diluted into medium so that final concentrationswere 5 nM, 10 nM, and 50 nM in each well. To determine the effect ofcompound A on osteoblast differentiation, MSCs (1×10⁶/ml) were firstcultured in medium in 24-well plates for 48 h. After allowing the cellsto adhere to the growth surface, the medium was gently removed and 100μl of each compound A dilution was added to 4 replicate wells.Osteoblast Culture Medium was then added (0.9 ml) and the cellsincubated.

For this study, osteoblast detection was performed using 2 differentmarkers. These were alkaline phosphase (AP) and osteocalcin (OC).Osteoblast detection required flow cytometry. Both markers wereconjugated to phycoerythrin (PE) which emits fluorescence light in the530 nm range.

After 14 days in culture, the medium of cultures was discarded. Thecells were harvested by incubation for 15 min at 37° C. with 10 mM EDTA,and cells

Those cells used for detection of AP+ osteoblasts were incubated for 45min with 10 μl of anti-human alkaline phosphatase-PE antibody at 4° C.After incubation, the cells were washed once with 4 ml of PBS andresuspended in approx. 400 μl of PBS for flow cytometric analysis.

The second set of cells were used to detect osteocalcin. The cells werefirst fixed in 4% paraformaldehyde for 10 min. and further incubated inPBS containing 0.1% saponin to permeabilize and maintainpermeabilization while the cells were incubated in the presence ofanti-human osteocalcin-PE monoclonal antibody for 45 min in the dark.The cells were washed with 2 ml of saponin-containing PBS andresuspended in approx. 0.5 ml PBS for flow cytometric analysis.

Results

FIG. 2 shows the effect of Compound A on osteoblast differentiation asdetected using both AP-PE and OC-PE. FIG. 2 shows the medianfluorescence intensity. The AP-PE marker indicated that with increasingCompound A doses, there is an increase in AP up to 50 mM. This increaseis above that obtained for the background or vehicle control. Therefore,Compound A results in a potentiation in fluorescence intensity ofalkaline phosphatase, which indicates stimulation of osteoblastdifferentiation from MSCs.

What is claimed is:
 1. A method for modulating stem cell proliferationand/or differentiation in a mammalian subject, which comprisesadministering to the subject in need thereof an effective amount of aprostaglandin compound represented by the formula (I):

wherein L, M and N are hydrogen atom, hydroxy, halogen atom, loweralkyl, hydroxy(lower)alkyl, lower alkanoyloxy or oxo, wherein at leastone of L and M is a group other than hydrogen, and the five-memberedring may have at least one double bond; A is —CH₃, or —CH₂OH, —COCH₂OH,—COOH or a functional derivative thereof; B is single bond, —CH₂—CH₂—,—CH═CH—, —C≡C—, —CH₂—CH₂—CH₂—, —CH═CH—CH₂—, —CH₂—CH═CH—, —C≡C—CH₂— or—CH₂—C≡C—; Z is

or single bond wherein R₄ and R₅ are hydrogen, hydroxy, halogen, loweralkyl, lower alkoxy or hydroxy(lower)alkyl, wherein R₄ and R₅ are nothydroxy and lower alkoxy at the same time; R₁ is a saturated orunsaturated bivalent lower or medium aliphatic hydrocarbon residue,which is unsubstituted or substituted with halogen, alkyl, hydroxy, oxo,aryl or heterocyclic group, and at least one of carbon atom in thealiphatic hydrocarbon is optionally substituted by oxygen, nitrogen orsulfur; and Ra is a saturated or unsaturated lower or medium aliphatichydrocarbon residue, which is unsubstituted or substituted with halogen,oxo, hydroxy, lower alkyl, lower alkoxy, lower alkanoyloxy,cyclo(lower)alkyl, cyclo(lower)alkyloxy, aryl, aryloxy, heterocyclicgroup or heterocyclic-oxy group; lower alkoxy; lower alkanoyloxy;cyclo(lower)alkyl; cyclo(lower)alkyloxy; aryl; aryloxy; heterocyclicgroup; heterocyclic-oxy.
 2. The method as described in claim 1, whereinthe stem cells are stem cells of human origin stem cells.
 3. The methodas described in claim 1, wherein the stem cells are progenitor cells. 4.The method as described in claim 1, wherein the stem cells are embryonicstem cells, somatic stem cells or combinations thereof.
 5. The method asdescribed in claim 1, wherein said prostaglandin compound is 16-mono ordihalogen-prostaglandin compound.
 6. The method as described in claim 1,wherein said prostaglandin compound is 15-keto-prostaglandin compound.7. The method as described in claim 1, wherein said prostaglandincompound is 13,14-dihydro-16-mono or dihalogen-prostaglandin compound.8. The method as described in claim 1, wherein said prostaglandincompound is 13,14-dihydro-15-keto-prostaglandin compound.
 9. The methodas described in claim 1, wherein said prostaglandin compound is13,14-dihydro-15-keto-16-mono or dihalogen-prostaglandin compound. 10.The method as described in claim 1, wherein said prostaglandin compoundis 13,14-dihydro-16-mono or difluoro-prostaglandin compound.
 11. Themethod as described in claim 1, wherein said prostaglandin compound is15-keto-16-mono or difluoro-prostaglandin compound.
 12. The method asdescribed in claim 1, wherein said prostaglandin compound is13,14-dihydro-15-keto-16-mono or difluoro-prostaglandin compound. 13.The method as described in claim 1, wherein said prostaglandin compoundis 13,14-dihydro-16-mono or dihalogen-prostaglandin E compound.
 14. Themethod as described in claim 1, wherein said prostaglandin compound is15-keto-16-mono or dihalogen-prostaglandin E compound.
 15. The method asdescribed in claim 1, wherein said prostaglandin compound is13,14-dihydro-15-keto-16-mono or dihalogen-prostaglandin E compound. 16.The method as described in claim 1, wherein said prostaglandin compoundis 13,14-dihydro-16,16-difluoro-prostaglandin E₁ compound.
 17. Themethod as described in claim 1, wherein said prostaglandin compound is13,14-dihydro-15-keto-prostaglandin E₁ compound.
 18. The method asdescribed in claim 1, wherein said prostaglandin compound is11-deoxy-13,14-dihydro-15-keto-16,16-difluoro-prostaglandin E₁ compound.19. A method for modulating proliferation and/or differentiation of stemcells of a mammalian subject, which comprises contacting said stem cellswith an effective amount of a prostaglandin compound represented by theformula (I):

wherein L, M and N are hydrogen atom, hydroxy, halogen atom, loweralkyl, hydroxy(lower)alkyl, lower alkanoyloxy or oxo, wherein at leastone of L and M is a group other than hydrogen, and the five-memberedring may have at least one double bond; A is —CH₃, or —CH₂OH, —COCH₂OH,—COOH or a functional derivative thereof; B is single bond, —CH₂—CH₂—,—CH═CH—, —C≡C—, —CH₂—CH₂—CH₂—, —CH═CH—CH₂—, —CH₂—CH═CH—, —C≡C—CH₂— or—CH₂—C≡C—; Z is

or single bond wherein R₄ and R₅ are hydrogen, hydroxy, halogen, loweralkyl, lower alkoxy or hydroxy(lower)alkyl, wherein R₄ and R₅ are nothydroxy and lower alkoxy at the same time; R₁ is a saturated orunsaturated bivalent lower or medium aliphatic hydrocarbon residue,which is unsubstituted or substituted with halogen, alkyl, hydroxy, oxo,aryl or heterocyclic group, and at least one of carbon atom in thealiphatic hydrocarbon is optionally substituted by oxygen, nitrogen orsulfur; and Ra is a saturated or unsaturated lower or medium aliphatichydrocarbon residue, which is unsubstituted or substituted with halogen,oxo, hydroxy, lower alkyl, lower alkoxy, lower alkanoyloxy,cyclo(lower)alkyl, cyclo(lower)alkyloxy, aryl, aryloxy, heterocyclicgroup or heterocyclic-oxy group; lower alkoxy; lower alkanoyloxy;cyclo(lower)alkyl; cyclo(lower)alkyloxy; aryl; aryloxy; heterocyclicgroup; heterocyclic-oxy.
 20. The method according to claim 19, whereinsaid composition is contacted with the stem cells in vitro or ex vivo.